Opiate addiction is now a national epidemic marked by an increased incidence of abuse and overdose of heroin and elevated misuse of prescription opioids which also bears a high incidence of overdose death. Despite this growing opiate problem there remains a lack of knowledge about the molecular neuropathology of this human disorder. A fundamental core of our reverse translational research efforts has thus been to fill critical gaps of knowledge by direct investigation of the brains of human heroin abusers. Such efforts have identified the transcription factor ets-like kinase 1 (ELK1) as a central candidate in human heroin abusers. ELK1 disturbance was downstream of the mu opioid receptor (the pharmacological target of heroin metabolites and prescription opiates) and mitogen-activated protein kinase (MAPK) pathway and it was found by in silico analysis of microarray data to target the promoters of a large percentage of down-regulated genes in the nucleus accumbens (NAc) of heroin abusers. Surprisingly, very limited knowledge exist about ELK1 in relation to drug abuse, but this transcription factor has been implicated in other fields in cellular differentiation and synaptic plasticity that are highly relevant to the pathophysiology of addictio disorders. We hypothesize that heroin abuse leads to dysregulated ELK1-mediated transcriptional activity of target genes involved in the reorganization of striatal synapses and tht modulate drug-seeking behaviors. We propose: (1) to determine ELK1-mediated transcriptional regulation in neurons within striatal and mesocorticolimbic brain regions of human heroin abusers by conducting ELK1 ChIP in combination with high throughput sequencing (ChIP-seq) on the nucleus accumbens, dorsal striatum and medial orbitofrontal cortex of heroin abusers. This data will also be integrated with transcriptome analysis to determine the relationship to gene expression. (2) To identify the epigenetic landscape across the ELK1 gene that contributes to its dysregulation in heroin abusers. (3) To investigate the causal role of ELK1 in structural plasticity and heroin seeking behavior by use of animal models. The multidisciplinary approach will expand significant insights about novel targets for treatment interventions and the dataset accrued by this body of work will be a unique and valuable resource to the field given the current lack of such human brain data.